From Population Variance to Standard Error

The fill weights on a production line have population variance $\sigma^2 = 45 \text{ g}^2$.

A technician repeatedly draws independent random samples of $n = 20$ items and records each sample's mean weight $\bar{x}$.

Recall that

$\text{Var}(\bar{x}) = \frac{\sigma^2}{n}$

Across these repeated samples, what is the standard deviation of the sampling distribution of $\bar{x}$?